1. Technical Field
The present invention relate to an anti-expansion joint bridge and, more particularly, to an anti-expansion joint bridge which eliminates an expansion joint structure from an upper structure thereof, and includes a plurality of slidable steel plates to cover a space between girders or floor slabs expanding and contracting on piers and asphalt concrete pavement on the steel plates, so that expansion and contraction of the girders occurring on the piers is prevented from affecting the pavement, thereby ensuring smooth travel of vehicles thereon.
2. Description of the Related Art
It is estimated that the first bridges were made by humans in prehistoric times. These bridges probably took the form of a tree trunk, a wisteria vine, or the like fallen across a river or a valley and were developed from there. It is assumed that in early bridges, cut tree trunks were transported and installed across valleys or rivers. If a single tree trunk was not long enough to span the required distance, several tree trunks then began to be used and, over time, handles or railings were fixed to these early bridges.
Since early bridges were made of natural materials using the characteristics thereof, it is assumed that girder bridges constructed of wooden logs or bridges built from various vines were the first to be built, followed by stone bridges later on.
Generally, a bridge structure expands and contracts depending on load and temperature variation. Thus, the bridge structure, particularly, an upper structure of the bridge, is constructed to a predetermined length or more and has a regular spacing formed between sections thereof (referred to as a ‘gap’). An expansion joint device is mounted to the spacing in order to prevent the bridge deck structures from being damaged and to ensure that a vehicle can travel smoothly thereupon.
As such, the expansion joint device, called an expansion joint, is provided to absorb internal stress and prevent breakage of the bridge structure when a material expands and contracts as temperature changes. Typically, such an expansion joint is designed based open previously calculated amounts of expansion and contraction.
However, such an expansion joint has drawbacks of consuming considerable time to construct and complicating a process of paving the bridge with asphalt or concrete.
Further, the expansion joint degrades driving comfort when a vehicle passes over a bridge and is the most likely portion of the bridge to be damaged.
Furthermore, damaged expansion joints are difficult to repair or replace, and during maintenance work, if any, repairmen face considerable danger and traffic congestion may occur.
Here, difficulty in repair or replacement of expansion joints is due to the fact that an anchor bar of the expansion joint is firmly welded to an iron piece embedded in the concrete.
Further, since the expansion joint has substantially the same length as the width of the bridge and has a variety of shapes such as a toothed shape, a slight difference in height from a region near the expansion joint and from the pavement, or unevenness thereof causes vehicles traveling at high speed to be subjected to direct impact, which causes both the extension joint and vehicle tires to be easily damaged and broken.
As such, floor slabs, which constitute an upper structure of the bridge structure, have a gap therebetween, and the expansion joint mounted in the gap has been variously developed up to now.
Particularly, in South Korea, in the course of a project to expand the highway system, huge bridge structures were intensively constructed in the 1980s and 1990s, and rail-type expansion joints which have an expansion allowance of 160 mm-320 mm were typically mounted to bridges constructed during this period. However, expansion joints as currently constructed are subjected to breakage or damage at the rail or lower support structure thereof due to deterioration and external pressure or shock caused by vehicles travelling thereon. Such broken or damaged expansion joints must be frequently replaced.
A conventional expansion joint structure of a floor slab for a bridge structure is shown in FIG. 1. The expansion joint structure includes non-contracting concrete slabs 3, 3′ which are fixed by anchor iron pieces to face each other in an upper cavity defined by floor slabs 2, 2′ which are coupled to each other and face each other, steel plates 4, 4′ which are separated from each other and are fixed to each other by anchor bolts in an upper recess defined by the non-contracting concrete slabs 3, 3′, and a flexible expansion joint 10 which is mounted to connect upper portions of the opposite steel plates 4, 4′.
The expansion joint 10 is provided at the surroundings with expansion/contraction grooves 5 which are spaced from the steel plates and defined by connecting the steel plates 4, 4′ with each other. The expansion joint 10 is mainly formed of rubber.
In the conventional expansion joint structure constructed as described above, if the floor slabs 2, 2′ and the non-contracting concrete slabs 3, 3′ expand or contract due to temperature variation, the expansion/contraction grooves 5 of the expansion joint near the steel plates 4, 4′ absorb the expansion or contraction of the floor slabs 2, 2′ and the non-contracting concrete slabs 3, 3′, thereby causing the expansion joint 10 to expand or contract.
However, the conventional expansion joint structure has a problem in that the presence of the expansion/contraction grooves 5 on the expansion joint 10 rattles when vehicles travel thereover, thereby degrading driving comfort. That is, the conventional expansion joint structure has an uneven and irregular upper surface, thereby significantly deteriorating driving comfort.
Further, the expansion joint 10 located on top of the bridge structure is likely to be broken due to load applied during vehicle passage, and the load applied to the upper portion of the expansion joint 10 is focused upon one end of the expansion joint 10 as well, thereby causing breakage of the end of the expansion joint 10.
Moreover, the expansion/contraction grooves 5 also cause further breakage of the end of the non-contracting concrete slabs 3, 3′ since the grooves are located between the non-contracting concrete slabs 3, 3′.
That is, when a vehicle passes over the expansion/contraction grooves 5, rattling shock occurs and is transferred to the end of the non-contracting concrete slabs 3, 3′, which increases the likelihood of breakage.
If defects such as breakage, failure, or the like occur on such an expansion joint, water leakage occurs and a bridge seat structure supporting the floor slab of the bridge becomes rusty, resulting in fatal damage. In this case, rust stains on a capping stone on a pier detract from the appearance of the bridge and cause concrete structures to be subjected to severe fracture and breakage.
Particularly, if a portion of the non-contracting concrete slabs 3, 3′ is damaged, assembly of the expansion joint 10 becomes defective, thereby causing bridge failure and exposing the pier to a danger of collapse.
Further, since the expansion joint 10 exposed through the expansion/contraction grooves 5 is likely to suffer from breakage owing to load applied by vehicles travelling thereover and internal stress caused by expansion and contraction of the non-contracting concrete slabs 3, 3′, the damaged expansion joint 10 must be frequently replaced, thereby causing considerable costs associated with replacement of the expansion joint 10.